Advancing age is associated with a decline in functional status and an increase in the prevalence of chronic medical conditions. Disturbed nighttime sleep is also a common finding in older individuals. Epidemiologic data indicate that more than 50% of the adults over the age of 65 years have some form of a chronic sleep-related complaint. Numerous studies have documented that disruption of nocturnal sleep architecture is associated with daytime sleepiness and alterations in neuroendocrine function. Although studies with overnight polysomnography have examined the changes in sleep architecture with increasing age, the distinct effects of healthy aging and age-associated illnesses have not been rigorously investigated. The major objectives of this application are to describe the age-related changes in sleep architecture in the general population. Using the baseline polysomnographic data collected by the Sleep Heart Health Study, the current application will employ novel analytical techniques including multi-state survival analysis and spectral analysis to characterize the macro- and micro-alterations in sleep architecture across the age spectrum. The Specific Aims of this application are as follows: (1) To characterize the independent effects of healthy aging on sleep micro-architecture in a community-based sample of middle-aged and older adults without medical co-morbidity; (2) To delineate the independent effects of sleep apnea on nocturnal sleep micro-architecture in middle-aged and older adults; and (3) To examine the combined effects of aging and sleep apnea on nocturnal sleep micro-architecture. The research proposed in this application will offer a unique perspective on sleep in the aging adult from the most extensive collection of polysomnographic data. Segregating the effects of normal aging from age-associated illness will identify potential sources of variability in sleep that occurs in older adults. Moreover, a comprehensive summary of the changes in sleep structure with increasing age will provide the necessary foundation for ongoing studies of aging cohorts to determine whether disruption of sleep architecture plays a significant role in the age-related predisposition to cardiovascular, metabolic, and neurobehavioral consequences. [unreadable] [unreadable]